The Wordfast philosophy is strictly try-before-you-buy, which is why
a generous demo mode is offered. You can freely download and install the regular,
full version of Wordfast Classic from the
download page.
Once this is done, you can start using Wordfast Classic with all its features
activated, except these demo limitations:

The Translation Memory (TM) will hold only about 1000 translation units. When the limit
is reached, a message will tell you; at that point, you can create a new, empty translation
memory(1) and
keep translating.

Links to Machine Translation (MT) will only work for two or three segments in a session.

The demo mode is not time-limited. Many translators work for weeks before deciding
to buy. However, if you want to use Wordfast for a real job with a larger TM, do not
postpone buying the license until the last minute because purchasing a license takes
some time: typically a few hours (credit card payment) or several days (bank wire transfer).

_____________________________________________________(1)You can even turn your current TM into a BTM (see the manual), or
compress all TUs that were not re-used, to reduce the TM size and continue working.